This invention relates generally to improvements in water purification systems of the type having a reverse osmosis (RO) unit or the like for removing dissolved ionic material and other contaminants from an ordinary supply of tap water or the like. More particularly, this invention relates to an improved control valve for a reverse osmosis water purification system, the control valve for positively and preferably sequentially terminating pure water production and brine outflow to a waste or drain when a pure water reservoir reaches a substantially filled condition.
Water purification systems in general are well-known in the art of the type having a reverse osmosis (RO) unit or membrane for converting an incoming supply of ordinary tap or feed water into relatively purified water for use in cooking, drinking, etc. In general terms, the reverse osmosis unit comprises a semi-permeable RO membrane through which a portion of the tap water supply is passed, such that the membrane acts essentially as an osmotic filter to remove dissolved metallic ions and the like as well as other contaminants and undesired particulate matter from the tap water. In normal operation, these impurities are removed from one portion of the water flow to produce relatively pure water, with the removed impurities being concentrated in another portion of the water flow, commonly referred to as retentate or brine, which is normally discharged as waste to a drain. The thus-produced flow of relatively purified water is available for immediate dispensing for use, and/or for temporary storage within a suitable reservoir or vessel awaiting dispensing for use. A pure water dispense faucet mounted typically on or adjacent to a kitchen-type sink or the like is manually operable to dispense the produced purified water. While the specific construction and operation of such RO water purification systems may vary, such systems are exemplified by those shown and described in U.S. Pat. Nos. 4,585,554; 4,595,497; 4,657,674; and 5,045,197.
Reverse osmosis water purification systems of this general type rely upon a minimum pressure differential across the RO membrane to produce purified water. In this regard, this pressure differential is relatively maximized when a pure water storage reservoir is substantially empty, but progressively decreases as the pure water storage reservoir fills. Decreased pressure differential across the RO membrane has inherently resulted in a decreased volume of produced purified water. When the pure water storage reservoir reaches a substantially filled condition, prior art systems have generally functioned to turn the system “off” by closing or attempting to close a tap or feed water inflow valve, to halt system water flow-through and thereby minimize associated water waste in this “off” condition. Alternative proposals have envisioned a retentate or brine flow shut-off valve to halt system water flow-through while the system is “off”. However, these approaches undesirably leave unflushed concentrated contaminants at an upstream side of the RO membrane, whereat these contaminants can migrate through the RO membrane to the pure water side while the system is in the “off” condition. Accordingly, desirable minimization of waste water has been accompanied by undesirable potential contamination of the produced pure water.
There exists, therefore, a significant need for further improvements in and to reverse osmosis water purification systems, and particularly with respect to an improved control valve wherein water waste is substantially eliminated when a pure water reservoir reaches a substantially filled condition, but wherein such reduced water waste is not accompanied by any significant contamination of the already-produced pure water. The present invention fulfills these needs and provides further related advantages.